Mutations in the PINK1 gene are linked to an autosomal recessive early onset familial form of Parkinson's disease (PD). The molecular and physiological functions of PINK1 that generate pathological abnormality of PD-associated PINK1 mutants are largely unknown. .Therefore, we have developed a genetic model of PD in Drosophila to study the in vivo role and genetic interactions of PINK1 with known and new potential contributors to this disease. We have recently shown that inactivation of Drosophila PINK1 (dPINKI) using RNAi results in progressive loss of dopaminergic (DA) neurons and in ommatidial degeneration of the compound eye, which is rescued by expression of human PINK1 (hPINKI). Moreover, expression of human superoxide dismutase 1 (SOD1) suppresses neurodegeneration induced by dPINKI inactivation, and treatment of dPINKI RNAi flies with antioxidants (e.g., vitamin E) significantly inhibits ommatidial degeneration. Thus, PINK1 may normally prevent neurons from undergoing oxidative stress, a potential mechanism by which a reduction in PINK1 function leads to PD-associated neurodegeneration. Therefore, in this proposal we hypothesize that PINK1 plays a critical role in maintaining survival of dopaminergic neurons via a regulated pathway involving protection against oxidative stress. PD-pathogenic PINK1 mutants impair the functional pathway and therefore lose the ability to protect neurons from oxidative stress. In this study, we will take advantage of our newly-developed PD fly model (published in PNAS) to first investigate the genetic mechanisms and interactions that influence the severity of the PD pathogenic phenotype produced by PINK1 mutations under different (oxidative) stress conditions. The fact that wild-type human PINK1 but not disease-associated PINK1 mutations can reverse PD-associated pathologies in our fly model provides us with the opportunity to efficiently screen in a whole animal system for genetic and chemical modifiers that are likely relevant to finding therapeutics for this disease. We propose to screen for new genetic factors as well as for chemical compounds that can alter (e.g., ameliorate or aggravate) the neurodegenerative phenotype observed in our PD fly model.